Conventionally, photolithography has been used to manufacture semiconductor devices. However, as semiconductor devices are downscaled, the resolution of photolithography is becoming insufficient and pattern formation is becoming difficult. Therefore, in recent years, nanoimprinting is beginning to be used instead of photolithography.
In nanoimprinting, a template for nanoimprinting is constructed by making an unevenness in the surface of a quartz substrate by selectively removing the surface of the quartz substrate to form alignment marks for alignment and a pattern (a device pattern) which is an inverted pattern of the resist pattern to be formed on the semiconductor substrate. Then, an ultraviolet-curing resist material is coated onto the semiconductor substrate to be patterned; and the template is pressed onto the resist material. Continuing, the resist material is cured by irradiating ultraviolet through the template onto the resist material while the template is pressed. Thus, the resist pattern is formed by the device pattern of the template being transferred onto the resist material. Because nanoimprinting has few causes of fluctuation such as the depth of focus, aberration, exposure amount, etc., that are problematic in conventional photolithography, many resist patterns can be formed exceedingly easily and with good precision by constructing one template.
However, the manufacturing of semiconductor devices includes processes in which a new pattern is formed on a substrate on which a pattern is already formed. In the case where nanoimprinting is used in such a process, it is necessary for the alignment of the template with respect to the substrate to have high precision. Such alignment is performed by overlaying the alignment marks formed in the template and the alignment marks formed on the substrate while viewing with visible light.
However, because the refractive index with respect to visible light of quartz which is the material of the template is substantially equal to the refractive index with respect to visible light of the ultraviolet-curing resist material, the alignment marks can no longer be seen when the template is pressed onto the resist material and the resist material enters the recesses of the alignment marks. Therefore, the alignment unfortunately cannot be performed with sufficient precision.